The latest dilemma for all of us is 26” or 27.5” wheel size. Can’t decide? Want to try them both without spending loads of money on a new frame & wheels etc? At DMR we've found a solution.
The difference in radius between the two sizes is about 12.5mm, so we’ve been testing prototypes of a rim bed spacer that fits a bit like a tire onto the 26” rim and increases the diameter to the 27.5 tire seat diameter and provides a new rim profile on top. Working name is the DMR 20switchinch and it has a rigid outer rim with the flexible ‘liner’ fitting bed that is mechanically locked to the ‘receiver’ rim & also further clamped by air pressure (actually a significant amount of force is exerted over the area around the circumference).
Fit the 20switchinch, fit new tires and tubes and providing your frame and fork has clearance for 27.5 tires you are good to go. Naturally the system is for Disc brake use only. We’ve been testing on a couple of widths and it will work over a tolerance of 4mm - inner rim width of 19 - 23mm. The prototype system adds about 200 grams per wheel, but we expect to save up to 70 grams on the production version. The floor of the 27.5 rim bed is tubeless ready with the bead hook feature built in.
Testing so far has been going well with Olly Wilkins riding DH in Madeira.
Still early days but we are hoping to have it available later this summer for around £27.50 each.
We are also prototyping a 27.5” to 29” and a “narrow to fat bike” version, but we are not convinced on the size of this future market yet.dmrbikes.com